application forms are specific to each consulate. This is the link from the thai consulate in Hanoi's website
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You can also get the application when you get there. Remember they will need copies of your data page of your passport, your current entry stamp to vietnam and a passport sized photo.
A 90 day single entry Non-Immigrant Type ED visa is $80 US dollars <- that's the ONLY currency they take at the thai consulates there for the visa.